Electrical current transformers are generally an integral part of some circuit breakers. For example, one type of transformers is included in ground fault circuit breakers, which are commonly used to protect people from electrical shocks due to line-to-ground current flow through a person's body. Ground fault circuit breakers are required to detect current flow between line conductors and ground at current levels on the order of about 5 milliamperes. These low current levels are much below the overload current levels required to trip conventional circuit breakers. In response to detecting of a ground fault current, the circuit breaker is tripped to prevent further flow of current through the protected circuit. Specifically, a movable contact of the circuit breaker is separated from a fixed contact to prevent further current flow.
The primary windings for this type of transformer are the conductors of the distribution circuit being protected. Specifically, the conductors are encircled in a transformer housing core. For example, in a two-pole circuit breaker three conductors are routed through an opening in the transformer housing: two line conductors (i.e., line one and line two) and the neutral conductor. In a three-pole circuit breaker four conductors are routed through the opening: three line conductors and the neutral conductor.
During normal conditions, current flowing in one direction through a line conductor will return in the opposite direction through the neutral conductor. This produces a net current flow of zero through the transformer and, accordingly, a multi-turn winding provides no output. If, however, a fault is established between one of the line conductors and the ground, more current will flow in one direction through the transformer than in the other direction, producing a current imbalance. The current imbalance produces uncancelled flux in the transformer's core, resulting in an output in the multi-turn winding that trips the circuit breaker mechanism.
One problem associated with some transformers is that conductors and/or terminal assemblies cannot be properly routed through the transformer housing. For example, in some transformers the routing of a conductor may be possible only before any terminals or lugs are welded to the conductor. Such assembly restrictions result in difficult and rigid assembly methods, which are likely to increase manufacturing time and cost.
Another problem associated with some transformers, is that the physical position of the conductors and/or terminal assemblies cannot be accurately controlled within the space of the transformer through which they are being routed to achieve a required level of milliamperes sensing. Accordingly, the functionality and/or reliability of the transformer can be greatly reduced.
What is needed, therefore, is a transformer housing for a circuit breaker that addresses the above-stated and other problems.